hi everyone, new to the forums, just bought this truck and the owner pulled both tanks off and put a new single tank on it, none of my gauges work but im more worried about my gas guage, any ideas on what might be wrong? also, they put a flat bed on it with utility tool boxes and they put the tail lights in the boxes, so to me it looks like a wiring nightmare......not completly stupid but not real good with electrical systems.....thanks in advance for any info

 

Hi romeowhisky, and welcome.
If it isn't too much trouble could you tell us exactly what gauges you have and which are working and which are not. Some instrument panels had separate voltage regulators for the gauges , some had the regulator built into the temp gauge and some worked other ways also. Some had fuses for the gauges. So as you can see there were a lot of variations to deal with and at least for me it could get a little confusing. With the right info to start with we may be able to suggest a solution or solutions.
Just as some people should never own a car, some should not attempt to do simple electrical work. We had a gent at one time whose theory was to tie all the wires in a bundle and chuck them back in the dash and they would sort themselves out. Sometimes his work went like a ball of fire!!
We should be able to help you with the light wiring provided, they didn't try to do too much, with too little.

 

speedometer works but its off about 5mph, temp does not work, gas goes to full with the engine running but drops to half when you turn it off, it has an aftermarket oil pressure that seems to work, aftermarket tach that seems to work but im sure its not completely accurate, the gas and temp is my primary concern, all the lights on the truck work and the radio works...from the little bit of research ive done it says the wiring for the gas gauge has an open circuit thats why its constantly showing full, does this sound right? but at the same time im not sure exactly what to look for since they pulled both tanks off and put a new single tank on it, im hoping all i have to do is put a new sending unit in it and run new wires from it up to the gauge? or just replace the voltage regulator?........also, my odometer does not work......its like my whole panel is dead except for my speedo, which isnt completely accurate anyway, i really dont want to fork out a ton of money to take it to someone to rewire everything

 

Its been a while since I worked on an 87 and I'll do the best i can. I think your best bet will be to remove the instrument cluster. If I remember correctly the gauges were able to be replaced independently and were of the push in variety. What you might do for starters would be to trace the wires from the fuel gauge through the plug and get the color of those two wires.One should come from the regulated voltage supply for the gauge and the other should come from the fuel tank sending unit. You may need to do a little detective work to see just what they did with the wires from the dash that switched from one tank to the other. If I recall when the sending unit wire was grounded the gauge would peg over to full. If there is a hot supply to the temp gauge that sometimes contained the voltage regulator for all the gauges. The same was true for the temp gauge . If you grounded the wire from the temp sending unit it pegged the temp gauge to hot. Try those two tests and let us know what you get.

 

if that flat bed was welded to the frame and not bolted to it then some of the wires could have been burned and giving you a big headache. and you may have to do some checking but if one removed and did away with the front tank then it's a safe bet that it needs to have some way of closing that circuit for the tank that they took out and did away with

 

Thanks guys, ill look into tracing my wires but can only do it on weekends cuz the truck is still sitting down at my dads, the flat bed is wooden and just bolted down to the frame

 

ok well i didnt have any success, im not real smart about anything other than simple tune ups and brakes, im just gonna get some aftermarket gauges and have my buddy throw them on for me...he said he does it all the time on diesel trucks and it would be easier for him to do that then trace down all the wiring through the whole panel, i dont know though but thanks for the info